In microelectronic applications, polymers that demonstrate high temperature resistance are generally well known. Precursors of such polymers, such as polyimide precursor polymers and polybenzoxazole precursor polymers can be made photoreactive with suitable additives. The precursors are converted to the desired polymer by known techniques such as exposure to high temperatures. The polymer precursors are used to prepare protective layers, insulating layers, and relief structures of highly heat-resistant polymers.
Negative-working photosensitive compositions containing high temperature resistant polymers have been disclosed in, for example, DE-A-2,308,830; DE-A-2,437,348; EP-A-0 119,162, or EP-A-0 624,826, U.S. Pat. No. 5,486,447, U.S. Pat. No. 5,856,065 and U.S. Pat. No. 6,010,825. The polyamide resist resin in these disclosures contained pendant olefinic groups, which can be crosslinked upon action of irradiation of suitable wavelength, thus forming a negative pattern. While these systems had good imaging properties (high sensitivity, high contrast, low unexposed film loss), some of them (DE-A-2,308,830; DE-A-2,437,348; EP-A-0 119,162, or EP-A-0 624,826) employed organic solvents as developers, which creates environmental concerns during device manufacture.
Furthermore, the prior art photosensitive compositions containing high temperature resistant polymers used NMP (N-Methyl-2-pyrrolidone) as a solvent. Since it has been established that NMP has detrimental effects on the performance of chemically amplified 248 and 193 nm photoresists (U.S. Pat. No. 6,277,546 B1; “Influence of Polymer Properties On Airborne Chemical Contamination of Chemically Amplified Resists”, W. D, Hinsberg, S. A. MacDonald, N. J. Clecak, C. D. Snyder, and H. Ito, SPIE vol. 1925, pp. 43–52, 1993), use of NMP-containing compositions is prohibited in many semiconductor fabrication facilities where such chemically amplified resists are used.
There are examples in the literature of positive working photosensitive formulations of highly heat-resistant polymer precursors, which contain no NMP and developable in alkaline developer (U.S. Pat. No. 4,339,521, U.S. Pat. No. 5,449,584, U.S. Pat. No. 6,127,086, U.S. Pat. No. 6,177,225 B1, U.S. Pat. No. 6,214,516 B1). While these inventions address the environmental concerns they sometimes exhibit inferior imaging properties such as low contrast and somewhat high dark erosion.
The purpose of this invention is to provide a negative working photosensitive composition suitable for making high temperature resistant patterns, which would have excellent imaging properties, contain no NMP and employ environmentally acceptable aqueous base solutions as developer.